1. Field of the Invention
The present invention relates to air presses in papermaking machines, and, more particularly, to multi-roll cluster arrangements used in such air presses.
2. Description of the Related Art
Effective water removal from a paper web is essential to the papermaking process. Various types of presses, using some combination of juxtaposed rolls, have been used for some time now for water removal. Such presses rely on the hydraulic pressure created at the nip between each pair of juxtaposed rolls through which the paper web travels in a given press configuration to drive water from the paper web.
Various press have been developed which have attempted to add an element of a positive air pressure within the press assembly to more effectively force the water from the paper web. With respect to roll presses specifically, the rolls of the press have been configured to form a chamber with a positive air pressure being supplied therewithin.
However, the effectiveness of a multi-roll air presses is limited by the degree to which the air chamber thereof can be sealed. The areas of the press where sealing becomes quite crucial are those areas where the paper web and the fabric(s) carrying it do not pass, as the web/fabric(s) combination inherently acts to seal the region of each nip through which it passes. Those regions of the air press through which the paper web/fabric(s) combination does not pass are the opposed lateral ends of each nip and the opposed chamber ends defined by the two sets of roll ends associated with the air press. Consequently, an end seal mechanism is provided at each chamber end, each such mechanism having a seal member which contacts each of the roll ends associated with that particular chamber end.
However, the ability of the end seal mechanism to efficiently seal a chamber is predicated on the seal member maintaining contact with each of the roll ends of that chamber end. If the roll ends are not aligned with one another, the seal member can come out of contact with at least one of the roll ends and thereby create a leakage site in the seal.
What is needed in the art is a system for maintaining alignment of each roll end set in order to promote full contact of an adjacent end seal mechanism therewith.
The present invention provides a multi-roll air press in which each end of a first roll is all provided with a bevel plate and each end of a second roll adjoining the first roll is provided with one of a seal ring and a gasket assembly, each bevel plate mating with the one of a seal ring and a gasket assembly in a manner that helps hold an end of the first roll in alignment with a corresponding end of the second roll.
The invention comprises, in one form thereof, an air press for pressing a paper web. The air press is composed of a plurality of rolls including at least a first roll and a second roll. The first roll and the second roll are positioned adjacent one another and form a first nip therebetween. Further, the first roll and the second roll each have a roll end, the roll end of the first roll adjoining the roll end of the second roll. A bevel plate is attached to the roll end of the first roll, the bevel plate having at least a first angled plate face. A seal ring is positioned adjacent the roll end of the second roll, the seal ring being juxtaposed to the bevel plate. The seal ring has at least a first angled ring face, and the first angled ring face mates with the first angled plate face.
In another form thereof, the invention comprises an air press for pressing a paper web. The air press is composed of a plurality of rolls including at least a first roll and a second roll. The first roll and the second roll are positioned adjacent one another and form a first nip therebetween. The first roll and the second roll each have a roll end, the roll end of the first roll adjoining the roll end of the second roll. A bevel plate is attached to the roll end of the first roll, and the bevel plate has at least a first angled plate face. A replaceable wear assembly includes a gasket, the gasket being attached to the roll end of the second roll. The gasket has a first beveled gasket edge, and the first beveled gasket edge mates with the first angled plate face.
An advantage of the present invention is that the interlocking of the rolls of the air press in a cross-machine direction maintains corresponding roll ends in alignment during operation the press, and such alignment is a precondition for minimizing leakage through the lateral seals of the air press.
Another advantage is a bevel plate and an adjoining cap seal ring can be configured to key into one another, promoting good sealing and alignment therebetween and substantially preventing any cap roll cover bulge and/or roll width variations from affecting the seal area therebetween.
Yet another advantage is the cap seal ring and the cap roll cover can be engineered to minimize and/or accommodate any stress build-up therebetween.
An additional advantage is that the compressibility of the floating cap design ensures that a seal can be achieved even if there is misalignment internally between rolls, by accommodating misalignment of roll ends.
A further advantage is an adjustable loading system can be supplied that is capable of continually applying a smallest possible force on the rolls needed to maintain a seal, even if the air pressure to be sealed against should change, thereby causing as little wear as possible to occur between a bevel plate and an adjoining cap seal ring.
A yet even further advantage is that a pneumatic expansion tube and/or a spring can be used in conjunction with the cap seal ring to help ensure contact and thus sealing of the cap seal ring with an adjoining bevel plate.
An additional advantage is that a gasket assembly with a replaceable gasket can be used instead of a cap seal ring, the gasket generally being more readily replaced than an entire cap seal ring.